Vapor space corrosion inhibited compositions

ABSTRACT

An inhibitor consisting of a mixture of at least one fatty acid amide and of at least one amine salt of a C8-C10 acid has been found to give synergistic vapor space rust inhibition with lubricating oils. The total inhibitor concentration ranges from about 0.01 to about 5.00 weight percent basis lubricating oil weight with the fatty acid amide to acid amine salt ranging from 1:1 to 1:10.

United States Patent White et al. July 1, 1975 VAPOR SPACE CORROSION INHIBITED 3.398.095 8/1968 Judd 252/341 x COMPOSITIONS 3,419,494 12/1968 Teeter et al. 252/34] [75] Inventors: zgggf gg i g gfg a Primary Examiner-Helen M. S. Sneed Platte droves a Tex Attorney, Agent, or Firm-T. H. Whaley; C. G. Rios;

Henry W. Archer [73] Assignee: Texaco Inc., New York, NY.

[ 22] Filed: Aug. 15, 1973 [57] ABSTRACT 21 App] 3 3 77 An inhibitor consisting of a mixture of at least one fatty acid amide and of at least one amine salt of a C -C acid has been found to give synergistic vapor [58] i 252/34 7 The total inhibitor concentration ranges from about 0.01 to about 5.00 weight percent basis lubricating oil '[56] References Cited weight with the fatty acid amide to acid amine salt f :l t 1:10. UNITED STATES PATENTS rangmg mm 1 0 2,820,013 1/1958 Chapman et al 252/34.7 x 10 Claims N0 Drawings VAPOR SPACE CORROSION INHIBITED COMPOSITIONS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to novel corrosion inhibiting compositions which have particular utility in preventing vapor space rust.

It has been observed that steam turbine lubricating oil systems frequently exhibit severe corrosion of the metal surfaces not normally submerged in the oil. This corrosion is normally called vapor space rust. Such corrosion is observed in the oil sump and oil return lines of many steam turbines. This vapor space rusting is undesirable because the rust particles break loose from the metal surface and cause filter plugging and reduce oil flow. Undesirably, the rust particles can reach the bearings, reduction gears, and governors thereby causing extensive damage and costly down time. The use of vapor space rust inhibitors, which coat the metal surface and prevent rusting, offers a promising solution to vapor phase rust inhibition problems.

2. Description of the Prior Art Some degree of vapor space rust inhibition has been obtained from suitable members of the following types of compounds: aliphatic and aromatic acids; primary, secondary and tertiary amines; amine salts of organic acids; and alkylomines. US. Pat. No. 2,775,560 covers the use of aliphatic monocarboxylic acids containing from 8 to 10 carbon atoms as vapor space rust inhibitors in turbine oil formulations. In the literature, combinations of normal carboxylic acids (C to C with selected low molecular weight aliphatic amines have been used as vapor space rust inhibitors. Up to now this combination of acids and amines has not been suggested in the patent literature as vapor space rust inhibitors.

SUMMARY OF THE INVENTION In accordance with the invention, it has been found that improved vapor space corrosion inhibition can be obtained by the addition to various lubricating oil compositions of a corrosion inhibiting amount of a mixture of at least one fatty amide, formed from the reaction of unsaturated fatty acids containing 12 to carbon atoms and diethanolamine, with at least one amine salt of a C8-C1" acid. The total inhibitor concentration ranges from 0.01 to 5.00 weight percent basis mineral oil with the preferred range being from 0.05 to 0.50 weight percent. The ratio of fatty amide to acid-amine salt ranges from 1:1 to 1:10 with the preferred ratio being 1:2 to 1:6. Uniquely, only unsaturated acids are effective.

Of the acids mentioned above the straight-chain mono or diunsaturated monocarboxylic acids (C -C are preferred for reacting with diethanolamine. Suitable amines include normal, branched and cyclic aliphatic amines; primary, secondary, teritary and saturated heterocyclic amines having twelve carbon atoms or less in the alkyl group or groups. The acid part of the amine salt can be a C C or C acid.

SYNTHESIS OF TALL OIL ACID-DIETHANOLAMINE Equimolar amounts of Tall Oil Acid and diethanolamine were cut back with approximately xylene, andthe mixture was heated at reflux until the calculated quantity of water was recovered fro the desired reactions. The reaction mixture was then stripped to a constant weight yielding the desired product.

The amide has the following structure:

R=C mono and diunsaturated hydrocarbon.

SYNTHESIS OF DECANOIC ACID-t-BUTYLAMINE SALT Equimolar amounts of the acid and t-butylamine were heated together, with 10% methanol dilution, for 2 hours at l20130F. The methanol solvent was then removed by nitrogen stripping at atmospheric pressure, yielding the decanoic acid-t-butylamine salt. Other decanoic acid-amine salts were prepared by a similar method. The amine salt has the following structure:

R=C H EXPERIMENTAL RESULTS Table I shows results obtained with a combination of a fatty acid amide and a fatty acid amine salt.

Each of the individual additives was first evaluated as vapor space inhibitors separately and then compared to combinations of additives. The total concentration of additive(s) was the same in all cases, either 0.10 or 0.15 wt.

The inhibited oil blends were evaluated in a modified version of the Hot Plate Reflux Rust Test 1 where the hot plate was replaced with a constant temperature oil bath. Metal specimen were composed of SAE 1018 mild steel. The specimen were polished using 240 grit abrasive and stored under precipitation naphtha until they were used. After the test was completed, the specimen were rated according to the amount and type of rust present. The following ratings were used:

1. ASTM Publication. 65th. Annual Meeting, Symposium on Turbine Oils (1962).

gr-l2 lll Blends containing the individual additives had unsatisfactory ratings in the test. However, the blend containing decanoic acid had a much better rating than blends containing the other individual additives. The addition of a small amount of the fatty amide to oil blends containing decanoic acid combined with either t-butylamine or tributylamine gave synergistic effects in inhibiting vapor space rust as shown by the explanatory data presented in Table I. It can be readily seen that the combination of any two of the three components will not provide equivalent vapor space rust protection to oil blends. In order to have the noted improvement in vapor space rust inhibition, an oil blend must contain the fatty amide, a fatty acid, and an aliphatic amine. The acid and amine should be reacted together prior to being used to form an acid-amine salt.

Further, it can be seen that only fatty amides prepared from unsaturated acids are effective. Both the amide prepared from hydrogenated Tall Oil Acid and the amide prepared from stearic acid had unsatisfactory ratings when added to oil blends containing octanoic acid combined with tributylamine. By contrast, the amide prepared from Tall Oil Acid had improved vapor space rust protection when added to oil blends containing octanoic acid combined with tributylamine as shown by the explanatory data presented in Table 1.

TABLE 1 VAPOR SPACE RUST TEST RESULTS OF INHIBITED TURBINE OILS Additive Wt. 71 Additive Rusting' Hrs/210F Tall Oil Acid-diethanol 0.10 S

amide (TOA-DEA) 0.15 insoluble Decanoic acid 0.10 T, L

0.15 2L t-Butylamine 0.10 38 0.15 2M.S Tributylamine 0.10 S 0.15 S Decanoic acid/t-butylamine 0.10 T. 2L (DAtertBA) 0.15 T, 2L Decanoic acid/ 0.10 38 tributylamine (DATA) 0.15 M. Decanoic acid/TOA-DEA 0.10 3M 0.15 3L TOA-DEA/ DA tert BA 0.10 3NR 0.15 3NR TOA-DEA/DATA 0.10 2T, L 0.15 2T. L TOA-DEA/octanoic acid/ tributylamine (OATA) 0.15 2T. L TOA-DEAV OATA 0.15 L M,S Stearic acid-diethanolamide/ DATA 0.15 3S In Turbine Oil qualified against MlL-L-1733|F specification.

NR Nu Rust, T-Trace. l.-Light. M-Moderate. S-Severe. A No Rust to trace rating was considered a passing result. The numbers show the no. of tests run. Prepared from hydrogenated Tall Oil Acid.

Pairs of amides and acid salts which give substantially equivalent results as the pairs exemplified in Table I included the following:

Tall Oil Acid-diethanolamide Palmitic acid-diethanolamide Oleic acid-diethanolamide Linoleic acid-diethanolamide Continued Acid Amine Salt Decanoic acidmorpholine Decanoic acid-N-methylmorpholine Diethanolamide Other additives can be used in usual amounts with the lubricants to which the vapor phase corrosion inhibitors of the invention are added. Such additives include extreme pressure agents, anti-clogging agents, antirust agents, oxidation inhibitors and the like.

The base oil for the additives of this invention can be any mineral hydrocarbon oil but usually is a turbine oil, a hydraulic oil or a drawing oil.

What is claimed is:

l. A lubricating oil composition having improved vapor space corrosion properties consisting of a corrosion inhibiting amount of a mixture of at least one amine salt of a C C aliphatic monocarboxylic acid together with at least one amide of diethanolamine and a fatty acid containing from 12 to 20 carbon atoms, the ratio of amide to acid amine salt being from about 1:1 to about 1:10, the balance, a major amount of a mineral hydrocarbon oil.

2. The composition of claim 1 wherein the concentration of said mixture ranges from 0.01 to 5.00 weight percent, basis oil.

3. The composition of claim 1 wherein the concentration of said mixture ranges from 0.05 to 0.50 weight percent, basis oil.

4. The composition of claim 1 wherein said mixture consists of Tall Oil Acid-diethanolamide and decanoic acid-t-butylamine.

5. The composition of claim 1 wherein said mixture consists of Tall Oil Acid-diethanolamide and decanoic acid-tributylamine.

6. The composition of claim 1 wherein said mixture consists of Tall Oil Acid-diethanolamide and decanoic acid-isobutylamine.

7. The combination of claim 1 wherein said mixture consists of palmitic acid-diethanolamide and decanoic acid-n-butylamine.

8. The combination of claim 1 wherein said mixture consists of oleic acid-diethanolamide and decanoic acid-morpholine.

9. The composition of claim 1 wherein said mixture consists of linoleic acid-diethanolamide and decanoic acid-n-pentylamine.

10. The composition of claim 1 wherein the ratio of amide to acid amine salt ranges from about 1:2 to

about 1:6. 

1. A LUBRICATING OIL COMPOSITION HAVING IMPROVED VAPOR SPACE CORROSION PROPERTIES CONSISTING OF A CORROSION INHIBITING AMOUNT OF A MIXTURE OF AT LEAST ONE AMINE SALT OF A C8-C10 ALIPHATIC MONOCARBOXYLIC ACID TOGETHER WITH AT LEAST ONE AMIDE OF DIETHANOLAMINE AND A FATTY ACID CONTAINING FROM 12 TO 20 CARBON ATOMS, THE RATIO OF AMIDE TO ACID AMINE SALT BEING FROM ABOUT 1:1 TO ABOUT 1:10, THE BALANCE, A MAJOR AMOUNT OF A MINERAL HYDROCARBON OIL.
 2. The composition of claim 1 wherein the concentration of said mixture ranges from 0.01 to 5.00 weight percent, basis oil.
 3. The composition of claim 1 wherein the concentration of said mixture ranges from 0.05 to 0.50 weight percent, basis oil.
 4. The composition of claim 1 wherein said mixture consists of Tall Oil Acid-diethanolamide and decanoic acid-t-butylamine.
 5. The composition of claim 1 wherein said mixture consists of Tall Oil Acid-diethanolamide and decanoic acid-tributylamine.
 6. The composition of claim 1 wherein said mixture consists of Tall Oil Acid-diethanolamide and decanoic acid-isobutylamine.
 7. The combination of claim 1 wherein said mixture consists of palmitic acid-diethanolamide and decanoic acid-n-butylamine.
 8. The combination of claim 1 wherein said mixture consists of oleic acid-diethanolamide and decanoic acid-morpholine.
 9. The composition of claim 1 wherein said mixture consists of linoleic acid-diethanolamide and decanoic acid-n-pentylamine.
 10. The composition of claim 1 wherein the ratio of amide to acid amine salt ranges from about 1:2 to about 1:6. 